Gravity wave generation and breaking observed with radiosondes at Ushuaia (Argentina)

PULIDO M AND H. TEITELBAUM

Proceedings of 8th International Conference on Southern Hemisphere Meteorology and Oceanography (AMS)

C. Nobre and C. Vera eds, INPE Brazil

Lugar: São José dos Campos: INPE, Brazil; Año: 2006; p. 623 - 632

High resolution radiosondes that were launched at Ushuaia (54.8$^o$S) during October-December, 1995 are examined. Episodes of high gravity wave activity are found in the lower stratosphere (from 10 km to 24 km). The enhancement of gravity wave activity is ascribed to the conjuction of two factors: gravity wave generation and Doppler-shifting. Two radiosondes with high wave activity cases are examined. They present inertio-gravity waves (IGW) with horizontal wavelengths of 400-700~km. Profiles of the Richardson number (Ri) present some patches where Ri descends bellow one quarter mainly induced by wave shear. These patches are identified as regions where IGWs are breaking. The possibility of gravity wave generation by orography and geostrophic adjustment are evaluated using the synoptic situation from ECMWF analyses and WRF simulations. We argue that synoptic waves propagating eastward over the Andes mountain range are generating the high wave activity events.